Hydroponic Tube LED grow light

How close should T8 lights be to seedlings? Most seedlings can be grown to transplant stage with high quality T8 ， but the lamps need to be kept close to the tops of the seedlings (less than one foot away) and these lights need to be run for 22 hours to get the DLI ideal for seedling growth of sun-loving plants.

New Design Grow Led Light 320W Quantum Board Grow 300W Led Grow Lights Greenhouse 400W Led Grow Light 300W grow light full spectrum dimmable